A primary witness in a court case that could see thousands of Australians pursued for online piracy has admitted to not preparing his own evidence.

The admission was made by prosecution expert witness Daniel Macek, a 30-year-old German technical analyst at MaverickEye. The firm's software was used to locate the IP addresses of alleged pirates who shared the film Dallas Buyers Club using a number of Australian internet providers, including iiNet.

The statement was "pretty much complete[d]" for him and he could not remember if he made any changes.

"You provide affidavits and statements in lots of litigations all around the world," Mr Lancaster said. "Is it your practice just to sign what is put in front of you?"

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"No," Mr Macek replied.

Mr Macek could not say whether he was authorised via email or letter to use the MaverickEye software to identify those who allegedly shared Dallas Buyers Club.

While it is not unusual for a witness not to prepare their own statement, iiNet may argue that because the witness had been billed as an "expert" his evidence should be dismissed.

Mr Macek was flown to Australia by Dallas Buyers Club LLC. It wants iiNet to hand over the account details of customers the studio alleges shared the movie on the internet without authorisation.

The prosecution claims it has identified 4726 internet protocol (IP) addresses belonging to customers of a number of Australian internet providers, including iiNet and Adam Internet, that shared the movie illicitly.

Dallas Buyers Club LLC wants iiNet and other providers to identify those customers and hand over email and residential addresses so that they can be pursued for damages. iiNet is resisting handing over the details, arguing the studio is likely to send "nasty letters" to their customers demanding large sums of money as it has done in the US.

The process of contacting infringers for damages is known as "speculative invoicing". In some jurisdictions judges have capped the amount of money studios can claim.

But Dallas Buyers Club LLC counsel Ian Pike told the court the letters had recently been changed.